Dark Secrets (Undertale and Steven Universe Crossover)
by Friday Night 13
Summary: When a mysterious creature name Elena Echos comes to try to bring monsters back to the Underground. It's up to Frisk and her new friend Steven to stop her. Together have to work together to stop her. Even if it means fusion with each other. They both will soon find out a bit more of Elena and what she's capable of. It up to them both to either show mercy or fight.
1. Chapter 1

_**Arthur Note:**_ _ **My first time doing a crossover for Undertale. Defiantly a first time doing Steven Universe. Anyways I know in the past I got lot of people saying that my paragraph are too long. I hope that the paragraphs are a bit shorter. I'm doing it in a different way and previous way of what I did when I first got on here. I hope you like it. Just to give you a heads up there are going to be some OCs involve in the story.**_

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A young boy about fourteen went inside the red barn. The boy has black curly hair, a bit chubby, wearing a red with a big yellow star T shirt, a brown jacket zipped up halfway, blue jeans with two pockets on the side, and brown tennis shoes. The boy look around calling "Lapis, are you in here?!" Just then a green with a weird shape light green hair lady wearing a black suit and pants, green like sunglasses came up to the young boy. She said "Lapis, left for a moment." The boy said a bit disappointed "oh, do you know where she's at, Peridot?" Peridot shook her head saying "nope, all I know she needed to do some sort of duty that she had to do…" before she finish a blue lady with long water like wings, has dark blue eyes along with her short hair, wearing a black blouse and a black skirt.

She landed in front of the boy and Peridot. The boy smiled saying "oh hey Lapis, I was looking for you." Lapis look up saying with a smile "oh hello Steven, nice to see you." Steven walk up to Lapis saying "Lapis, will you fly me somewhere where I haven't been before." Lapis look at Steven and ask "why?" Steven shrugs saying "well I wanna do something different and want to go someplace new." Peridot look at Steven and ask "so is that why you came here to find her? So you could go somewhere different by having her fly you up in the sky?" Steven nods and Peridot began to laugh. Lapis said "I don't see why not. I mean I'm kind of bored anyways." Steven eyes lit up with excitement. Peridot look at Lapis and said "you can't be serious." Lapis ignore Peridot and help Steven to get on her back.

Lapis spread her wings out asking "okay. Are you ready?" Steven nods and soon Lapis began to run with lots of speed saying "okay, here we go!" Lapis flap her wings and the way they both went. Peridot just shook her head as she went back in the barn to sit on the red tractor for Steven and Lapis' return. Steven was having a grand old time seeing the clouds in the sky so close that he could touch it. Lapis ask "having fun?" Steven nods saying "I'm sure am." Lapis laughs as she flew a bit higher into the sky. Steven ask "so where are we going?" Lapis thought a moment saying "well there is this one city that I think would be kinda fun to visit." Steven said "great, let's go then." Lapis laughs saying "okay then." Lapis swoop down a bit lower so she could see where she's going. Steven however was hooting away and kept saying how great it is to be in the sky.

Just then without warning a strange creature came out from the clouds flew in front of Lapis and Steven, making Lapis stop to look at the creature. The creature has big white wings as if to be an angel wings, her skin is light greenish blue color, the hair is light blue very short, her eyes are two different colors one green and one dark blue, wearing a blue shirt with a black strap on the right side of the shoulder, and a long puffy green skirt. Lapis narrow her eyes saying "what are you doing here Elena Echos?" Steven was confused of how Lapis knew this creature. Elena said "I see we meet again, Lapis Lazuli." Lapis huffs and said "what do you want?"

Elena said "I was just flying by when I saw him. The son of Rose Quartz." Steven eyes widened asking "you know my mom?" Lapis said looking up at Steven for a moment "don't talk to her Steven, she's a treat." Steven was now confused than ever before. Elena smiled a little saying "we once worked together Lapis, now we are enemies." Lapis said "that's because you took my sister away from me." Steven look at Lapis and ask "wait, you have a sister?" Lapis sighs saying "not the time to talk about this." Elena said "true but I know who has her. You won't be able to reach her anyways." Lapis close her eyes saying "leave us alone, Elena." Elena said "I would like to but I think not." Just then Elena flew towards Lapis and Steven and bump Steven right off of Lapis. Lapis was about to go after him when suddenly she was hit by Elena's power and was knock out. Both Lapis and Steven fell till they both hit the ground pretty hard.

At that time, a young human girl with short brown hair, wearing a blue with a dark pink hooded jacket, blue jeans, and brown shoes playing with a small lavender spider. The small spider has long black picky tail hair, six eyes, six arms with two black legs, wearing a pink shirt with a dark purple bow on the shirt, and pink puffy pants with little black lines on it. The two girls were playing around when they heard a boy's screaming voice. The girls look up to see a boy with black hair and a strange blue creature falling down into the woods. The small spider said "we got to help them, Frisky." Frisk nods as they both ran in to see if the boy and the strange creature was all right.

It took the girls a little while till they saw the two lying on the ground whom fell earlier. The small spider ask "are they still alive?" Frisk went to check on the two and nods saying "yeah, but I think their unconscious." Just then the blue creature began to open her eyes, she could hear Frisk talking to the small spider. Once she was able to sit up, she was shocked to see Frisk and the small spider. The small spider turn and said "oh you're up. Good nice to meet you. I'm Mia. what's yours?" The blue lady said "I'm Lapis Lazuli, I'm a… wait… where's Steven?" Frisk guessed that Steven was the boy with black hair. "I think right here" she said. Lapis look over and saw Steven was knock out. "Oh no" thought Lapis, "hope he didn't…" she was interrupt by Steven's moaning. Frisk and Mia looked to see Steven began to get up.

Steven was able to stand and look to see Frisk and Mia not far from Lapis or where he's at. "Where am I?" he thought to himself. Lapis look up at Steven and ask "are you alright?" Steven nods as he turn to Mia then to Frisk, "who are they?" Mia smiled saying "I'm Mia, this here is Frisky my best friend." Frisk said "it's just Frisk, Mia likes to call me Frisky." Steven smiled saying "oh, I'm Steven Universe, that's Lapis Lazuli." Lapis began to get up but fell when she got so dizzy. Frisk ask as she and Steven ran to Lapis' side, "are you okay?" Lapis shook her head saying "she must of did something to cause this dizziness or something." Lapis stumble to sit straight saying "why do I feel this way?" Mia said seeing how Lapis is, "we better take her to your mommy, Frisky."

Frisk nods saying "yeah, that would be best." Frisk and Steven help Lapis up and all three of them slowly walk out of the woods. Frisk look at Mia who was ahead of them saying "Mia, go get mom and hurry." Mia nods as she ran off to get help. Frisk look at Lapis then at Steven asking "so what happen?" Steven explain the incident with Elena and what she did. Frisk shook her head saying "oh that's too bad. Well don't worry I'm sure mom will know how to help you Lapis." Lapis smiled weakly at Frisk as she lower her head. Frisk could see that Lapis was a bit weak and still dizzy. They made it out of the woods when they saw Mia coming back with a goat lady with long floppy ears wearing a long purple dress with a white symbol and a pearl necklace came up to look at Lapis. "Oh my" said the goat lady "that fall must have got you really weak. Come, I'll see what I can do." The goat lady stay behind Lapis to make sure Lapis won't fall down.

They all made it into the house and got Lapis in the living room. The goat lady got Lapis lying on the couch with a pillow behind her head. The goat lady said as she turn to Frisk, "my child, go get an ice pack and put it on this girl's head." Frisk nods as she ran in the kitchen to get an ice pack. Mia look up at the goat lady asking, "will she be okay, Miss. Toriel?" Toriel nods saying "as long she rest, she'll be fine." Steven came up to Lapis and smiled at her as he place his hand on her's. Lapis smiled weakly and began to close her eyes. Frisk came back with a blue ice pack and had a red cloth around the ice pack. Frisk carefully place the ice pack on Lapis' head. Lapis flinch a little but relax with that coolness of the ice pack. Toriel ask "how does it feel, dear?" Lapis said "feels really good. Is it alright if I close my eyes for a bit?" Toriel nods saying "of course dear, you need to rest anyways." Lapis closed her eyes with the coolness of the ice pack.

Truthfully gems like Lapis don't need to sleep but they can however pretend or just relax like Lapis is doing. Steven sighs as Toriel put her hand on Steven's shoulder saying "do not worry my child, your friend will feel better soon." Steven nods saying "yeah, thanks for all your help." Toriel smiled saying "your welcome." Toriel turn to Frisk and Mia and ask "why don't you two go upstairs and play with him. That way he won't worry too much of his friend." The girls nods and took Steven upstairs to Frisk's bedroom to hang out. Toriel went back into the kitchen to do some work.


	2. Chapter 2

In the meantime two skeletons one taller and one shorter were walking back home from their friend Alphys house. The taller skeleton wearing a brown leather jacket with an orange shirt inside, blue shorts, big red boots and scarf around his neck. The shorter one has white pupils inside his eyes sockets, wearing a blue jacket with a white shirt inside, black with two white stripe shorts, and two pink fluffy slippers. The two brothers were enjoying the cool autumn air. They came up to the white house with a wooden steps leading to the purple door. As the skeletons brothers walk inside, they were shock to find Lapis lying on the couch. Toriel came in and said "oh hello you two, great to see you both home again." Toriel turn to see what the two skeletons were looking at. She smiled saying "oh, Frisk and Mia both found this one along with her little friend in the woods. The poor thing is a bit dizzy from a long fall."

Sans ask "what kind of creature is she?" Toriel said "I don't know, I didn't ask since she's so weak. I think it may be a little while before she could recover." Papyrus shook his head saying "well whatever she is, I'm sure she'll get better soon." Toriel nods saying "Frisk and Mia are with her friend right now. I'll go get them so you could meet her friend." Sans and Papyrus both nodded their heads as Toriel went up the stairs to get the kids. After a moment, Toriel came down with the three kids running down the stairs. Steven was shocked to see two skeletons in the living room with Lapis. Papyrus turn and ask "is this the friend to that creature?" Toriel nods and Papyrus said "he's a human, well that's super excited." Steven said correcting Papyrus "I'm a half human and half gem. Lapis is a full water gem. She's my good friend." Frisk look at Steven with confusion so did Mia. Sans ask "what's a gem?"

Steven said "oh you see me and Lapis are the Crystal Gems in terms we live on Earth. Of course I have to because I'm half human. But, anyways we're suppose to protect humanity from Homeworld Gems who wants to destroy humanity. I'm still in training but Lapis had just join with us Crystal Gems." Sans nods taking all the information from Steven. Frisk ask "why do these Homeworld Gems wants to harm us?" Steven shrugs saying "I'm still learning so I really have no idea." Mia said "maybe we should show them what we're like." Steven said "I asked that too but Garnet told me that Homeworld Gems don't care. It's up to their Diamond leaders to destroy humanity or not. The only Diamond I knew wants to destroy Earth is Yellow Diamond." Everyone except Sans were pretty confused of what Steven meant but no one asked any further. Mia ask looking at Steven, "so do you live with these Crystal Gems?" Steven said "yeah, not Lapis & Peridot, they have their own home. There are three more and they the ones I live with."

Frisk ask "so who are these three you live with?" Steven answer "well I mention Garnet, she's the leader of the group. Second Amethyst, she well let's say likes to eat all the time especially at night." Papyrus gave Sans a look saying "that's sounds like someone I know who get a snack at night." Sans shrugs saying "heh, can't help myself." Steven continued, "the last one is Pearl, she's pretty protective over me. I understand since she's so close to mom." Mia said "I like that name Pearl. It's so pretty." Everyone began to laugh. Just then a doorbell was heard. Toriel went to the door and answer it. There stood a blue spider, has black spiky hair, six eyes and arms, two legs, wearing a black shirt with a red bow tie around the neck and red shorts. The spider said "mamma, isn't feeling well so she asked me if I can pick Mia up." Toriel nods saying "I'll have her come." Toriel call Mia over and Mia ran up to Toriel and said when she saw her brother, "oh hi Kyle, where's mommy?" Kyle said "she hasn't been feeling well today. So she's staying home to rest."

Toriel went into the kitchen and grab a plate of apple pie saying "here give this to your mother, I'm sure she'll enjoy it." Papyrus said before the two spiders left, "tell Muffet to feel better soon!" Mia and Kyle promised they will tell their mother they will. Once the two spiders left, Frisk look at Steven saying "that was Kyle, Mia's oldest brother." Steven nods then look at Lapis asking "is Lapis going to be okay?" Toriel walk up to Lapis saying "I'm sure she will. She needs rest." Steven smiled at Toriel saying "thanks for the help." Toriel smiled at Steven saying "anytime my child." Toriel and Papyrus both went into the kitchen while Sans walk up to Steven asking "so kid, what's your name?" Steven said "oh my apologies but I'm Steven Universe, this is Lapis Lazuli." Sans nods saying "cool, uh where are you two from?" Steven responded "we're from Beach City." Frisk turn saying "hey, me, Paps, and Coco went there once. We had a good time there. The pizza is pretty good." Steven said "wow, I must have been off on a mission or at home when you guys show up."

Frisk giggled saying "Sans didn't wanted to come." Sans shrugs saying "thought do the kid good to be with my two younger siblings." Steven nods saying "cool, I wish I seen you guys." Frisk said "we had a lot of people giving us strange looks. Especially the guy who owns the pizza shop." Steven laughs saying "yeah, he and his family runs that business." Sans look at Steven saying "so uh… kid. How did you got here in the first place." Steven was about to answer when Papyrus interrupt asking Sans, "Sans, where is Coco? I haven't seen her all day!" Sans said "oh, she's probably at her friend's house. She goes there a lot." Frisk knew where Coco is at but never told Sans or Papyrus where she's really at.

Steven ask "who's Coco?" Sans said "she's my little baby sister, you would like her. She really nice." Sans turn to join Papyrus and Toriel in the kitchen. Frisk said looking at Steven, "she known to be the Soul Keeper." Steven said "I heard about the Soul Keeper. Pearl explain that the Soul Keeper are suppose to protect souls from danger. Mainly the one with the soul of Determination." Frisk lower her head saying "she's right. Coco has rare power and she has one that will take her life if not careful. But I can't tell you that. Though I'm the one with the soul of Determination." Steven turn saying disbelief "no way, you're kidding right?" Frisk shook her head saying "I'm not." Steven widened his eyes saying "wow, I heard that a person with Determination is quite rare to find." Frisk nods saying "it is, also very dangerous if it's get's out of hand."

Steven ask "like what?" Frisk was silent for a long time before she spoke "The soul of Determination can be easily be possessed by a demonic demon. That happen once to me. Let's just say it didn't gone to well till Sans and Coco help me." Steven was now very confused of what Frisk was talking about. Just then Toriel call Frisk and Steven into the kitchen. The two kids ran into the kitchen to eat some spaghetti that Papyrus had made for them.

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 _ **Arthur Note:**_ _ **I hope this chapter made things a bit clearer. I had someone thinking Mia is Muffet but she's not. Though she may look like Muffet but she's the daughter of Muffet. Like I said I'm throwing in OCs in the story. Though Elena is going to be the important OC through out the story. So there's a hint. Anyways I'm glad that so many are beginning to read my story. Thank you!**_

 _ **P.S. Don't think any of my OCs are one of the Undertale Characters. I wanted to add them into the story. That's just how I am. Hope you won't get confused. Thank You.**_


	3. Chapter 3

After Steven and Frisk ate their spaghetti they went into the living room. Steven look at Lapis and sighs saying "I hope she'll be okay." Frisk nods then said "with mom and my two uncles watching her I'm sure she'll be fine." Steven smiled at Frisk with a bit of hope of expression on his face. Just then as Steven turn and happen to see a skeleton girl has long brown hair, her bangs off to the side covering her right eye socket, her left eye socket has a white pupil similar to Sans, wearing a green shirt, black skirt, and long black boots coming down the stairs. Steven asked as he saw the skeleton girl come down the stairs, "ah… who's that?" Frisk look to where Steven is looking at saying "oh that's the one we told you about. That's Coco." Steven ask in a whisper tone, "the Soul Keeper?" Frisk nods her head and Steven kept his focus on Coco.

Coco happen to spot Steven with Frisk and ask "who's this with you, Frisk?" Frisk answer "this is Steven, he and his friend Lapis fell in the woods so me and Mia help. Also mom helped too." Frisk show Coco where Lapis was lying at. Coco nods saying "hm… I see? I hope your friend get's better soon. Anyways where are you both from, Steven?" Steven said "we're from Beach City." Frisk nods saying "also their the Crystal Gems who protects Earth from Homeworld." Coco nods as if she had already heard of this before. That kinda creep Steven out. He wonder if Coco knew all about the Crystal Gems. Though he didn't say anything. Coco look over to see Papyrus was about to enter the living room when he saw her. "There you are, Coco" said Papyrus, "I was beginning to worry."

Coco smiled saying "you don't have to really? I was just boning around at my pal's place." Papyrus huffed angrily saying "Nyeh, you're as bad as Sans." Frisk and Steven both began to laugh though their teeths. Coco then respond with a wink "come on Paps, you don't need to dig up the fun." Papyrus groan in frustration when Sans came in saying "yeah Paps, I think you need to bark it up to the root." Papyrus yell "will you two quite it! Gah, am I the only one the responsible one around here!" Papyrus storm out of the room. Sans and Coco gave each other a high five before they began to talk. Steven said after he stop laughing, "man, your family are pretty funny." Frisk nods saying "yeah, I know. It's great to see them teasing each other now and then." Steven said "yeah I can see that." Just then the kids turn to see Lapis opening her eyes. Steven came up to Lapis and ask her if she was alright.

It took a while but Lapis finally spoke while rubbing her forehead, "I think so, at least I got a bit of rest." Steven nods saying "yeah, I was pretty worried." Lapis only smiled at Steven as she turn to sit on the couch. Frisk ask "how's your head?" Lapis said "it's not hurting like it was before and I'm not dizzy anymore." Steven smiled saying "that's great, you and I can meet new friends here." Lapis looked at Frisk then at Steven before she was going to ask where she is when Sans and Coco both came over. Sans said "I see you're feeling better." Lapis nods saying "yes, um… who are you?" Sans chuckled before he said "I'm Sans, Sans the skeleton, this here is my sister Coco." Coco put her hand out saying "please to meet you." Lapis smiled as she place her hand on Coco and both shook hands.

Once the girls stop shaking hands, Sans put his hand out to shake. Just when Lapis put her hand on Sans that's when she heard farting noise. Steven and Frisk both began to burst out laughing and Coco shaking her head at Sans. Lapis gave an odd look at Sans. Sans said showing a whoopie cushion on his bony hand, "the old whoopie cushion in the hand trick. It's always funny." Coco said put her arms together, "you and that whoopee cushion. I guess I shoulda never brought that." Sans laughs a little before saying "don't worry I do that to so many other around here too." Lapis just rolls her eyes as she kinda giggled at Sans' little prank. Frisk and Steven both stop laughing when Toriel came in. "Oh" she said, "I see you are awake, my dear." Lapis nods saying "thank you for letting me rest for a bit." Toriel nods saying "it was my pleasure." Lapis look at Steven saying "I think we better go. Don't want the other gems worrying about you." Steven sighs saying "oh man, I was just having fun." Toriel ask in concerned "are you sure you'll be able to fly?"

Sans ask "wait, she can fly?" Steven said nodding his head, "yeah, that's how we got here in the first place." Sans look at Lapis saying "well that makes sense." Lapis and Steven went outside with the others following behind them. Frisk look at Steven and said "I hope we meet again soon." Steven nods saying "yeah, me too." They both hugged each other before Steven got on Lapis back. Lapis close her eyes and soon her wing magically appear from her blue gem. Frisk and her family were in awe of what they saw. Just as Lapis was about to take off that is when Elena flew down and landed in front of Lapis and Steven. "I thought I took care of you two" Elena hissed. Lapis narrow her eyes saying "get out of my way." Elena laughs saying "you think I'll let you pass. You know what I…" before she finish she turn her attention to Frisk saying with a hiss "you…" Frisk back up with Sans and Toriel stepping in front of Frisk for protection. Coco step beside Frisk but kept looking at Elena wondering where she had seen Elena at before.

Elena saw that there was no way to get to Frisk without putting up a fight. So she turn back towards Lapis. "You and I once worked together, so hand him over." Lapis put Steven down and said putting her arms in front of Steven, "never, not after you've done to me and my sister. I will never ever forgive you, Elena Echos." Coco eye pupil disappear as she stood shock to hear that name. Elena huff saying "very well, I don't attend to fight. Though I'll get him and I'll get that girl as well." Elena look towards Sans and Toriel. She flap her wings and flew off towards the sky. Sans ask "you know her?" Lapis nods saying "yes, it's a long story." Steven said "maybe it's best if we stay here. She might knock us down like before." Frisk came out from behind Sans and Toriel asking "so is that how you two fell?" Lapis nods saying "yes, she's the reason we're here."

Toriel said "come, I'm sure the Crystal Gems don't mind you two staying with us for tonight." Lapis and Steven follow Toriel and Sans into the house. Frisk was about to go in when she saw Coco was in her deep thought. Frisk walk up to Coco and call her name but she wouldn't respond. Frisk call her name four times before she got Coco's attention. Coco's eyes pupil appear and she look at Frisk saying "oh sorry about that." Frisk ask "it's seems you knew what Lapis was talking about. Do you know Elena?" Coco sighs saying "I'll tell you later on tonight. Come on, don't want them to keep waiting around." Frisk giggled and the two girls went inside the house.


End file.
